The paradoxical behavioral plasticity of the visual acuity function will be examined in cats with a surgical section of the posterior corpus callosum at 21-22 days of age. This study will replicate pilot data indicating such plasticity when surgery is performed at 21-22 days but not when 15 days or less, and will estabilsh the plasticity as a robust phenomenon. Potential age limitations on the plasticity phenomenon will be explored by testing the acuity function in cats with surgeries before and after the age used for surgery in the pilot group. A theory will be evolved to account for the age effect on the occurrence of the plasticity. An alternative explanation for the plasticity will be explored through the use of acuity testing under monocular conditions. Two other behavioral functions, visual field perimetry and eye alignment, will be examined at the same time to determine whether plasticity will also occur, and if so, when. Correlative light microscope histology will be performed to determine if the collasum was cut, how much was cut, and the extent of possible incidental surgical damage that might compromise the results. This behavioral plasticity is not predicted by any other literature, indicating that the central nervous system may well be capable of change at later stages of development than previously expected. In addition, with the long period of lack of improvement prior to the appearance of this change scientists may be encouraged to look for improvement in cases of nervous system deficits of function for longer periods of time.